The snake genus Chironius Fitzinger, 1826 is endemic to the Neotropical region, occurring from Honduras to Uruguay and northeastern Argentina. Some species of the genus have taxonomic and/or nomenclatural problems, such as C. flavolineatus which lacks agreement in the literature about its authorship and type locality. Some researchers have been suggesting Jan (1863) as the author of the species since he first described C. flavolineatus based on two specimens. However, other researchers report that Jan's description is so incomplete that it is not possible to ascertain what snake he had in mind and therefore suggest Boettger (1885) as the author, since he was the first to provide a detailed description of the species. In the present study one of the syntypes of C. flavolineatus, supposedly destroyed in Second World War, was found. Thus, the taxonomic identity of C. flavolineatus was redefined, its lectotype was designated and the authorship of the taxa is attributed to Jan (1863).